• Earthquakes and Structures
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• v.15 no.6
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• pp.655-665
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• 2018

Shield tunnels are widely used throughout the world. However, their seismic performance has not been well studied. This paper focuses on the seismic response of a large scale model tunnel in compacted sand. A 9.3 m long, 3.7 m wide and 2.5 m high rigid box was filled with sand so as to simulate the sandy soil surrounding the tunnel. The setup was excited on a large-scale shake table. The model tunnel used was a 1:8 scaled model with a cross-sectional diameter of 900 mm. The effective shock absorbing layer (SAL) on the seismic response of the model tunnel was also investigated. The thickness of the tunnel lining is 60 mm. The earthquake motion recorded from the Kobe earthquake waves was used. The ground motions were scaled to have the same peak accelerations. A total of three peak accelerations were considered (i.e., 0.1 g, 0.2 g and 0.4 g). During the tests, the strain, acceleration and soil pressure on the surface of the tunnel were measured. In order to investigate the effect of shock absorbing layer on the dynamic response of the sand- tunnel system, two tunnel models were set up, one with and one without the shock absorbing layer of foam board were used. The results shows the longitudinal direction acceleration of the model tunnel with a shock absorbing layer were lower than those of model tunnel without the shock absorbing layer, Which indicates that the shock absorbing layer has a beneficial effect on the acceleration reduction. In addition, the shock absorbing layer has influence on the hoop strain and earth pressure of the model tunnel, this the effect of shock absorbing layer to the model tunnel will be discussed in the paper.

• Tunnel and Underground Space
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• v.15 no.3 s.56
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• pp.177-184
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• 2005

The Sapaesan tunnel, the longest twin tube tunnel (4km) in Korea with 4 lanes each, is under construction with two years of delayed schedule because of the strong opposition from environmental bodies. Therefore, maximizing the construction efficiency was needed in tunnel project to compensate for time delay. This study includes improvements in the construction of the Sapaesan tunnel such as increasing excavation length and changing excavation sequence. In this paper the system for predicting tunnel face ahead is also introduced. Bulk-Emulsion explosive and Cylinder-Cut method were adopted in tunnel blasting to increase the excavation length. Optimum tunnel excavation step was designed to make up delayed time. Tunnel foe mapping, TSP survey and geological prediction system using computerized jumbo-drill were performed fnr safe construction of long and large twin tube tunnel.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1358-1365
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• 2010

A case study deals with Squeezing behavior under tunneling. Squeezing stands for large time-dependent convergence during tunnel excavation. Squeezing can occur in both rock and soil as long as the particular combination of induced stresses and material properties pushes some zone around the tunnel beyond the limiting shear stress at which creep starts. Under squeezing rock conditions, If the support installation is delayed the rock mass moves into the tunnel and a stress redistribution takes place around it. On the contrary, if deformation is restrained, squeezing will lead to long-term load build-up of rock support. This paper shows analysis case mutually with monitoring and numerical analysis result of squeezing behavior of Pinglin tunnel in Taiwan.

• Wind and Structures
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• v.20 no.5
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• pp.643-660
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• 2015

The wind tunnel test of large-scale sectional model and computational fluid dynamics (CFD) are employed for the purpose of studying the aerodynamic appendices and mechanism on suppression for the vortex-induced vibration (VIV). This paper takes the HongKong-Zhuhai-Macao Bridge as an example to conduct the wind tunnel test of large-scale sectional model. The results of wind tunnel test show that it is the crash barrier that induces the vertical VIV. CFD numerical simulation results show that the distance between the curb and crash barrier is not long enough to accelerate the flow velocity between them, resulting in an approximate stagnation region forming behind those two, where the continuous vortex-shedding occurs, giving rise to the vertical VIV in the end. According to the above, 3 types of wind fairing (trapezoidal, airfoil and smaller airfoil) are proposed to accelerate the flow velocity between the crash barrier and curb in order to avoid the continuous vortex-shedding. Both of the CFD numerical simulation and the velocity field measurement show that the flow velocity of all the measuring points in case of the section with airfoil wind fairing, can be increased greatly compared to the results of original section, and the energy is reduced considerably at the natural frequency, indicating that the wind fairing do accelerate the flow velocity behind the crash barrier. Wind tunnel tests in case of the sections with three different countermeasures mentioned above are conducted and the results compared with the original section show that all the three different countermeasures can be used to control VIV to varying degrees.

• Geomechanics and Engineering
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• v.29 no.1
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• pp.41-51
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• 2022

Tunneling in rocks having the time-dependent behavior, causes some difficulties like tunnel convergence and, as a result, pressure on concrete lining; and so instability on this structure. In this paper the time-dependent behaviour of squeezing phenomenon in a large cross section tunnel was investigated as a case study: Alborz tunnel. Then, time-dependent behaviour of Alborz tunnel was evaluated using FLAC2D based on the finite difference numerical method. A Burger-creep viscoelastic model was used in numerical analysis. Using numerical analysis, the long-time effect of squeezing on lining stability was simulated.This study is done for primary lining (for 2 years) and permanent lining (for 100 years), under squeezing situations. The response of lining is discussed base on Thrust Force-Bending Moment and Thrust Force-Shear Force diagrams analysing. The results determined the importance of consideration of time-dependent behaviour of tunnel that structural forces in concrete lining will grow in consider with time pass and after 70 years can cause instability in creepy rock masses section of tunnel. To show the importance of time-dependent behavior consideration of rocks, elastic and Mohr-Coulomb models are evaluated at the end.

• Explosives and Blasting
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• v.31 no.1
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• pp.55-63
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• 2013

With increasing needs in power, Singapore is requiring stronger power transmission. Singapore Transmission Cable Tunnel is underground tunnel for transmission system installation such as 400 kV cable. This Transmission Cable Tunnel is 35 km long in total. The North-South Transmission Cable Tunnel is 18.5 km long and there is a total of three (3) contracts; NS1, NS2 and NS3 in respect of the design and construction. The East-West Transmission Cable Tunnel is 16.5 km long, and also there is a total of three (3) contracts; EW1, EW2 and EW3. Among of them, SK E&C has been awarded and operating contract EW2 and NS2. In scope of works, each contract has 3 to 4 shafts which connect aboveground and underground high volt cable and those shafts are used as TBM launching shafts during construction. Transmission Cable Tunnel is undercrossing middle of Singapore and most of shafts are located in urban area. Thus, optimal blasting design satisfying high blasting efficiency as well as blasting vibration limit of Singapore is highly required. Blasting design for large shaft of Singapore Transmission Cable Tunnel follows blasting vibration limits in Singapore and reflects our blasting engineering skills. With Singapore Transmission Cable Tunnel Contract EW2, it is expected that our excellent blasting engineering and performance skills can be delivered to the world.

• Journal of the Korea Safety Management & Science
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• v.25 no.2
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• pp.129-138
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• 2023

This study attempted to analyze the comparative advantage in terms of disaster safety costs in verifying the effectiveness and economic feasibility of the high-performance water-bulwark system in the pole tunnel, which was recently promoted as a part of the acceleration of vehicles. The tunnel to be analyzed was divided into a short tunnel(Anyang, Cheonggye) and a long tunnel(Suraksan, Sapaesan). As a result, it was analyzed that 25% of the improvement effect would occur if one lane was secured by applying the Water-Bulwark System. It was analyzed that this is because the time value cost, which accounts for a large proportion of the traffic congestion cost of short tunnels and pole tunnels, differs depending on the congestion time and traffic volume, not the length of the tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.325-337
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• 2021

On the road and rail tunnels, the evacuation pathway and facilities such as smoke-control and fire suppression system are essential in tunnel fire. In the long twin tunnels, the cross-connection tunnel is usually designed to evacuate from the tunnel where the fire broke out to the other tunnel. In twin shield tunnels, the segment lining has to be demolished to construct the cross-connection tunnel. Considering the modern shield TBM is mostly the closed chamber type, the exposure of underground soil induced by removal of steel segment lining is the most danger construction step in the shield tunnel construction. This case study introduces the excavation method using the thrust of large steel pipe and reviews the measured data after the construction. The large steel pipe thrust method for the cross-connection tunnel can stabilize the excavated face with the two mechanisms. Firstly, the soil in front of excavated face is cylindrically pre-supported by the large steel pipe. Secondly, the excavated face is supported by the plugging effect caused by the soil pressed into the steel pipe. It was reviewed that the large steel pipe thrust method in the cross-connection tunnel is enough to secure the construct ability and stability in soil from the measurement results about the deformation and stress of steel pipe.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.04a
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• pp.120-127
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• 2001

Long term earthquake observations at different tunnel sites within a variety of alluvial soil deposits have demonstrated that a circular tunnel is liable to deform in such a way that its two diagonal diameters crossing each other expand and contract alternately. Based on this knowledge, the soil-tunnel interaction and isolation effect for this particular vibration mode is investigated. Interaction effect is considered with the condition of fixed tangential strain between the tunnel and the soil. Isolation effect embodied by covering up the tunnel with isolation materials is discussed as a possible measure for mitigating seismic damage to it. When Poisson`s ratio of isolation material decreases or the shear modulus ratios of the soil to isolation material become large, the isolation effect becomes bigger.

• Wind and Structures
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• v.13 no.1
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• pp.57-82
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• 2010

The 486m-long roof of Shenzhen Citizens Centre is one of the world's longest spatial lattice roof structures. A comprehensive numerical study of wind effects on the long-span structure is presented in this paper. The discretizing and synthesizing of random flow generation technique (DSRFG) recently proposed by two of the authors (Huang and Li 2008) was adopted to produce a spatially correlated turbulent inflow field for the simulation study. The distributions and characteristics of wind loads on the roof were numerically evaluated by Computational Fluid Dynamics (CFD) methods, in which Large Eddy Simulation (LES) and Reynolds Averaged Navier-Stokes Equations (RANS) Model were employed. The main objective of this study is to explore a useful approach for estimations of wind effects on complex curved roof by CFD techniques. In parallel with the numerical investigation, simultaneous pressure measurements on the entire roof were made in a boundary layer wind tunnel to determine mean, fluctuating and peak pressure coefficient distributions, and spectra, spatial correlation coefficients and probability characteristics of pressure fluctuations. Numerical results were then compared with these experimentally determined data for validating the numerical methods. The comparative study demonstrated that the LES integrated with the DSRFG technique could provide satisfactory prediction of wind effects on the long-span roof with complex shape, especially on separation zones along leading eaves where the worst negative wind-induced pressures commonly occur. The recommended LES and inflow turbulence generation technique as well as associated numerical treatments are useful for structural engineers to assess wind effects on a long-span roof at its design stage.